The present invention relates to a polymeric dielectric material for use in high-energy density capacitors, a high-energy density capacitor made with the polymeric dielectric material and an integrated circuit package that comprises a high energy capacitor made with the polymeric material of the present invention.
Multiple layer printed circuit boards (PCBs) are used in computer systems for interconnecting integrated circuit (IC) chips and other electronic components and devices. A multiple layered printed circuit board is formed from a substrate supporting a plurality of insulated conductive trace layers. The insulated trace layers typically include surface conductive trace layers and embedded trace layers with selected trace layers connected as a ground plane and a power plane. Integrated circuits and electronic components and devices are mounted on an outer surface of the multiple layered printed circuit board by a variety of well-known techniques.
One problem arising with multiple layered printed circuit boards is that electronic operation of integrated circuits includes switching that results in high frequency fluctuations in the potential difference between the power plane and the ground plane. This problem has been addressed using bypass capacitors connected between the power plane and the ground plane and mounted in the general vicinity of each integrated circuit. As used herein, the term “bypass capacitor” is equivalent to the term “power conditioning capacitor.” The bypass capacitors are generally effective in reducing and stabilizing voltage fluctuations for low frequency voltage oscillations. Unfortunately, a via connection of a bypass capacitor to the power and ground planes introduces a small inductance that impedes the bypass function of a bypass capacitor and reduces the effectiveness of the bypass capacitor to stabilize voltage fluctuations at higher frequencies.
Types of power conditioning capacitor devices fabricated in printed circuit boards include surface mounted power conditioning capacitors and embedded power conditioning capacitors. A surface mounted power conditioning capacitor is typically mounted in conjunction with printed circuit board embodiments. The surface mounted power conditioning capacitor is positioned as closely as possible to the chip it protects.
Surface mounted power conditioning capacitors, such as is shown in one prior art embodiment at 20 in FIG. 4, have several problems as compared to embedded capacitors, one embodiment of which is illustrated at 30 in FIG. 3. One problem is that large numbers of surface power conditioning capacitors are needed to accommodate the current requirements and to reduce circuit noise. Also, surface power conditioning capacitors have resistance and inductance limitations, occupy considerable surface space, increase the number of solder joints and, therefore, reduce the system reliability.
Materials with high dielectric constants and low loss tangents have had use in solving these problems and in fabricating capacitors. Several high dielectric constant materials based upon polymers combined with ceramics are known. U.S. Pat. Nos. 4,335,180 and 5,358,775, owned by Rogers Corporation, describe composites of fluoropolymers, such as polytetrafluoroethylene, PTFE, and ceramics that have a high dielectric constant.
A high dielectric composite that comprises a matrix polymer wherein the matrix polymer includes an epoxy resin based on bisphenol F epoxy and an organic amino curing agent was described by S. Asai, et al., in IEEE Transactions on Components, Hybrids and Manufacturing Technology, vol. 16, No. 5, August, 1993. The polymer, which has a high dielectric constant, also includes a barium titanate filler at a 34 volume percent level.
NEC has produced a high energy density capacitor which is based on a carbon/sulfuric acid dielectric. The NEC device has a high capacitance that drops off rapidly with frequency.
These polymeric and ceramic-based materials generally have a problem with temperature stability. The dielectric constants of these high dielectric ceramic-based materials change with temperature. The change in dielectric constant changes the electrical properties of a component such as a capacitor.